Mono-halogen-substitutedthiophanthraquinone



Patented July 4, 1950 UNI ED STATES QFFICE].

MONO-HALOGEN-SUBSTITUTEDI. THIOPHANTHRAQUINONE;

vLouis Frederick Fieser, Belmont, Mass, and Her-H ma-n Elbert Schroeder, Wilmington, Deb, 'as signors to E. I: du Pont de Nemoursdv Company, Wilmington, Del., a corporation OfSDBlfla'.

ware

N D awin An lic oNe emhcr24 .1. 4l scrlalN 29 .4.-

This invention relates to chemical compositlons useful as valuable-intermediates inorganic synthesis; particularly-in the synthesisof dyestuiTs, and a newmethod for theirmanufacture. More p articularly this invention relates to a process of manufacturing-- pure monohalogenth-iophanthraquinonecompounds and still more particularly toa process for manufacturingcer-. tain monohalogeri-thiophanthraquinones hithertofore not obtainable. The compounds to which this invention particularlyrelates are halogenthioph'anthraquinones of the formula-:-

in which one of-the positions 3, 5; 6f,i 7, and; 8

is substituted by a halogen atom' consisting ofbromine and chlorine atoms;

T e: e m. h onh n hra u none is. emn oy n-theam n o r esccom ounds, n i Qi ri ina 7 n me.- sed ha 149 a d. Seer nnl 94,

131 9- 2) h 1ed the c r e pond n hydroa bon; compo nd? onhanthrace e-* The object of this invention istoprovide for a processornrociiicinahaloaensuhst t clr ionhe nthracuinoncs; hi her. y eld and. purity than,

byaany/ th rlsnowap c s Ai u fie -Q i to 1 prep r monashaloge -s1 b its1 =thiobh n+r hraquinones by a ocess Which-- pro eeds moo hly and; without degr dat n; f." the, thio: nhena'rni i us- Anot er objec s-t i ov de or a; proces ii-pr duc ng substan ial y pur mo o: halo cn-thiopha products contain littl 19 otherisom ric; om:

p s, A: ur he 'Q hicct is epare rt in;

monoahalo enethiop anthliflllll nq d i h ar not capable of isol i n; y: mi ther; known; A; st l v urther, object-is o. pro de; for;

process. the production of new: compositions of mat e namely =haloethiophanthraquinone and 'I-halo thiophanthraquinone.

As described? in the copending applicationot Lee and Weinmayr' United States. Serial Number 723 ,6733 certain thenoyl' benzoic acids= substituted; in the" benzene nucleus byhalogenacan be. ring-a.

.quinan s; which as finali closed to form corresponding thiophanthraquinones:

v M has As l rio s n h l nate i aha h quin nes quinone or '7 halo thigphanthraquinone by ring closing the corresponding halogenated thenoyl benzoic acids, due to the influence of reagents causing ring closure, rearrangements occur with the result that 5-halo-thiophanthraquinone and- '7--halo-thiophanthraquinone are not isolable from thelfinal product or capable of-identification.

When one attemptsfto prepare 6-halo-thio'ph-' anth-raquinonei and 8 halo thiophanthraqub none.i by. ring closingthe corresponding halothenoyli-benzoic acids, rearrangements; occur to a; somewhat lesser extentazbut-vnone the less final products of highest" purity. arenot obtained but containisomeric com-pounds'which are. separatedonly, with greatzdifficulty.

Mixtures of isomers are obviously less desirable than the pure materials for the synthesis of various dyestufiistructuresand there is therefore a great need: for a method which will'afiord the isomers desired in a high statev of purity suitable for further use.

We have nowfoundamethod of providing pure thiophanthraquinone and its halogenated deriv-,.

atives, in particular those which by ordinary methods of ringrqlosure. are inaccessible, which comprises reduction; of; a- 2g-(2sthenoy i-b o acid, to a 2,;- .(=2 1thenyl-) -l: e1 1 z,oic:- acid; rin rclosure" oi: 2-,CZa-thenyh)-benzoic acid to a 4-acetoxy=; thioph-anthrene and oxidation of; the 4z-racetoxy-c thiophanthrene to form the thiophanthraquinone particular utility in cases where more orthodox methods of preparation afford low yields with undesirable by-products. Since the thenoylbenzoic acid ring-closure cannot be relied upon for high yield of pure products, this new method offers the only route to certain desirable m'ate'rials.'-.

While it is surprising that the ring closure of the thenylbenzcic acids to acetoxythiophanthrenes proceeds so smoothly and without rearrangement, it is more noteworthy that the acetoxythiophanthrenes can be oxidized in such high yields to the thiophanthraquinones apparently without appreciable degradation of the thiophene nucleus.

The nature of our invention is more clearly demonstrated by the following examples. Parts are by weight unless otherwise specified.

Example 1 A solution of 19 parts of v 6-chloro-2-(2-thenyD-benzoic acid and 1.5 parts of freshly fused zinc chloride in 114 parts of acetic acid and '76 parts of acetic .anhydride was refluxed for 90 minutes, and then whilestill hot, carefully dilutecl to about double its volume with water. Upon filtration parts of 4-acetoxy-5-chlorothiophanthrene, melting point 80-85 0., was obtained. After a crystallization from methanol it melted at 8788 C.

One part of 4-acetoxy-5-chloro-thiophanthrene was dissolved in'20 parts of glacial acetic acid and oxidized by adding 0.1 part of chromic acid anhydride at room temperature, heating the solution to 80 C. and adding again 0.9 part of chromic acid anhyride. The charge was then refluxed five minutes, diluted with 4.5 parts of 36% hydrochloric "acid and refluxed one minute longer. After water had been added to the hot solution until a precipitate began to form, the solution was cooledand filtered. The 5-chlorothiophanthraquinone (0.665 part) was purified by vatting it in alkaline sodium hydrosulfite (yellow vat), and precipitating from the filtered solution with air. *It was crystallized'from acetic acid, and then from methanol and melted at l71.5'1-'72.5 0. Analysis indicates that this material is a mono-chloro-thiophanthraquinone different in melting point from any of the pure mono-chloro-thiophanthraquinones described in copending application Serial Number 723,673; which shows :a pure product melting at 224 C. and no lower melting isomer. A mixture with the product of Example 2 (the 8-isomer-melting point 224 C.) shows little depression but melts over a wide range This is undoubtedly the first preparation of substantially pure 5- chloro-thiophanthraquinone,

which has not been described previously. It should be noted that this material cannot be separated in a pure form from the 8-isomer by the usual fractional crystallization procedures.

Example 2 A charge of 20 parts of 3-ch1oro-2-(2-thenoyl) benzoic acid, 900 parts of 28% aqueous ammonia, 05 part of copper-sulfate crystals, and 50 parts of zinc dust was heated at the boil for 36 hours, with 45 parts of 28% ammonia added every six hours. The charge was then clarified with adsorbent carbon (Nuchar), filtered, and the colorless filtrate was acidified while still hot. Upon cooling and filtration, 18 parts of 3-chloro-2-(2- thenyD-benzoic acid, melting point 109-112 C., was obtained.

A solution of 16 parts of 3-chloro-2- (2;- thenyl)-benzoic acidand'lfi parts freshly. fused zinc chloride in 96 parts of acetic acid and 64 parts of acetic anhydride was refiuxed for 9 0.-

minutes. and then carefully diluted while still hot to about double the volume'with water. Theprecipitate was filtered at room temperature and dried. 4-acetoxy s-chloro-thiophanthrene $15 parts, melting point 178-l80- C.): was obtained... After crystallization from methanol, it meltedat The oxidation of one part of .t-acetoxy-El- Example 3' A charge of 4.5 parts of 5-chloro-2-(2-thenoy l) benzoic acid, 200 parts of 28% aqueous ammonia, 0.12 part of, copper sulfate crystals, and 11.3 parts of zinc dust was heated to the boil. Eleven (11) parts of 28% ammonia was added six times in six-hour intervals, while slight refluxing was maintained. One part of adsorbent carbon (Nuchar) was then added, and the charge was filtered and acidified with acetic acid while still hot.

Upon cooling 3.92 parts of 's-cmoro-z- (2-thenyl) benzoic acid was obtained (92% of theory), melt-- ing point 133 C. The product was purified by dissolving it in 300 parts of dilute ammonia and precipitating it again by adding acetic acid to the boiling solution. Upon cooling pure 5-c'hloro- 2-(2-thenyl)-benz'oic acid was obtained as long. white, felted'needles, melting point 134 C.

A charge of 3.3"parts of 5-chloro-2-(2-thenyl-v benzoic acid, 20 parts of glacial acetic acid, 14 parts of-acetic anhydride, and 0.4 part of freshly fused zinc chloride was refluxedfor minutes;

Water was added carefully to the charge until' heavy crystallization set in. Upon cooling-2.8

parts of 4-acetoxy 6-chloro -.thiophanthrene,

melting point of 146-147 C., were. obtained- (77.8% of' theory); After two crystallizations frc m 5ov parts of ethanol each timeitnwasob-j tained with :the constant "melting Ipoint 1 of 154 Five and two tenths (5.2) parts of -acetoxyfi-ohloro-thiophanthrene were dissolved in 110 parts of glacial acetic acid. About one-half part of chromic acid anhydride was added and the charge was heated, to 80 where 4.5 parts of chromic acid anhydride were added at once. After refluxing for a few minutes, 30 parts of concentrated hydrochloric acid were carefully added, and :boilingv was =.continued affew minutes longer. water were then :added, and \the :crystalline' precipitate was filtered iatzroomitemperature. The filter cake was washed acid-free .and dissolved in .700 parts .of water .of 160 eon'taining 12 parts of sodium hydroxide and15 parts of sodium hydrosulfite. The filtered solution was blown with airuntil all-bf the =6-c hloi-'o-.thiopl'ianthaquinone had been precipitated, .Thus 3.6 parts of .6- chloro thiophanthraquinone (77.0% yield), melting ,point o'f 182 were obtained. Upon crystallization from250 parts of high boilingg'asoline, and again from 100 parts of 'chlorobenzene it was obtained as .yellow crystals with the constant melting point'of 189- 190 C. This appears identical with the product from ring-closure of the 4-(or 5) -chloro-2-(2- thenoyl) -b.enzoic acids.

Example 4 A charge of 2.64 parts of 4 -ch1oro 2 (2- thenoyl)-benzoic acid, 120 parts of 28% aqueous ammonia, 0.07 part of copper-sulfate crystals, and 7 parts of zinc dust was heated to the boil. Seven ('7) parts of 28% ammonia were added to the mixture at six-hour intervals while refluxing was continued. The ammoniacal solution was filtered and acidified with acetic acid while still hot. The crystalline precipitate was filtered at room temperature, and purified by dissolving it in hot dilute ammonia and again precipitating it with acetic acid. 4-chloro-2- (Z-thenyl) -benzoic acid, melting point of 155 0., was obtained (2.22 parts, 88.8% yield) in the form of short, coarse needles. A mixed melting point with 5-chloro-2-(2-thenyl) -benzoic acid showed a strong depression.

One and twenty-five hundreds (1.25) parts of 4-acetoxy-l-chloro-thiophanthrene were added to 30 parts of glacial acetic acid and oxidized with 1.25 parts of chromic acid as described in the preceding example. The crude 'l-chlorothiophanthraquinone was purified by vatting it in 100 parts of water containing four parts of sodium hydroxide and five parts of sodium hydros-ulfite. 7-chloro-thiophanthraquinone (0.75 part, 67% yield, melting point 208 C.) was obtained. After crystallizations from high boiling gasoline, ure I-chloro-thiophanthrao1uinone melted at 213-214 C. A mixture of the 7- chloro-thiophanthraquinone and the 6-chlorothiophanthraquinone of the preceding example melted from 180 to 198 C. This product is therefore the new and previously undescribed '7-chloro-thiophanthraquinone and is an isomer which apparently cannot be obtained by ringclosure of the chloro-thenoylbenzoic acids; nor can it be separated in pure form by fractional crystallization of a mixture with the 6-isomer.

In the above examples one may in each instance replace the starting material, chloro-2- (2-thenoyl)-benzoic acid, with bromo-2-(2- thenoyl)-benzoic acid and thus prepare 5, 6, 7, or 8 bromo-thiophanthraquinone with the same Two hundred and 'lfifty (250) =pai1tsio'f advantageous results of purity of compound. Qne may also use the above-described process to prepare :a thiophanthra'quinone substituted in'the '2 or 3 position:by bromine or chlorine by ch'oosing asa starting material '-a 2-(2- thenoyl) benzoic acid which" contains -a-chlorine or bromine constituent -iILithe 4 or :5 position of the thiophene ring. The results ob tained here :also give the desirable purity of products.

The thenylbenzoic acids'employed in this invention are prepared by reduction of the corresponding thenoyl derivatives by usual methods, of which the zinc-ammonia reduction is particularly eifective. Ring-closure of the anthranyl acetate; is best accomplished in an organic acid medium, e. g, acetic acid, using at least one mole equivalent of anhydride such as acetic anhydride and an acidic catalyst such as anhydrous zinc "chloride to effect the desired reaction which Qmay'be. represented as Oxidation is very conveniently effected with such common agents as chromic acid or sodium dichromate, preferably in an acid medium. The oxidation may also be accomplished by suspending the anthranyl acetate in aqueous or alcoholic alkali and oxidizing with air or with sodium hypochlorite, but the yields under these conditions are not as high.

As can be seen from the above description our invention affords a very convenient method for preparing the pure thiophanthraquinone substituted in 2, 3, 5, 6, '7, or 8 positions by bromine and chlorine. It ofiers the only known method for preparing isolable 5- and 7-halogenated thiophanthraquinones. To summarize we have discovered a process for reparing pure monobromo and mono-chloro-thiophanthraquinones which because of the unsymmetrical nature of their chemical structure, if prepared by any other known method of synthesis contain inseparable isomers in which case they would not be as desirable as the pure compounds for use as dye intermediates.

We claim:

1. The method for preparing pure halogensubstituted-thiophanthraquinone of the formula:

0 wherein one of the positions 2, 3, 5, 6, '7, and 8 is substituted by a halogen of the group consisting of bromine and chlorine, which comprises reducing the corresponding mono-halogen-substituted 2-(2-thenoyl) -benzoic acid to a 2-(2-theny1) benzoic acid, ring closing to a 4-acetoxy-thiophanthrene, and oxidizing to the desired product.

2. The method for preparing a pure monohalogen-substituted-thiophanthraquinone of the formula:

wherein one of the positions 5 and 7 is substituted by a halogen of the group consisting of bromine and chlorine, comprising reducing the corresponding halogen-substituted 2 (2 thenoyl) benzoic acid in the presence of ammonia and zinc to a 2-(2-thenyD-benzoic acid, ring closing to a 4-acetoxy-thiophanthrene, and oxidizing to the desired product.

4. A mon'o-halogen-substituted-thiophanthra-# quinone of the formula:

v I o in which one of the positions 5 and 7 is substituted by a halogen of the group consisting of chlorine and bromine.

5. 5-ch1oro-thiophanthraquinone. 6. '7-chloro-thiophanthraquinone. i LOUIS FREDERICK FIESER. HERMAN ELBERT SCI-IROEDER.

REFERENCES CITED The following-references are'of record in the file of this patent: v

Thomas, Anhydrous Aluminum- Chloride, pages 540, 544and 547, Reinhold Pub. 00., 1941.

Bernthsen and Sudborough, Organic Chemistry, Van Nostrand, N-.-Y., 1925 (1922 edition), page .9. 

4. A MONO-HALOGEN-SUBSTITURED-THIOPHANTHRAQUINONE OF THE FORMULA: 